Switch location for an undersik heater.

[MidAtlantian]

Hi,
I am installing an "instantaneous" undersink water heater in a utility room, and will run a separate cable from the consumer unit. I know I need to have a double pole switch to turn it off, and that the switch must be within 2 meters of the heater.

But there are natural stone tiles, large ones, above the work surface that I do not want to disturb. Can I place the switch in the cupboard under the sink? As a 2nd option, could I place the switch on the front of the cupboard?

Lastly, the consumer unit is RCD protected. Do I need additional 30ma RCD protection for this circuit?

Thank you,

 

[Chri5]

As long as you can safely access the switch inside a cupboard is ok. Don't mount it on the base, on the side wall on the door open side at the front is best.

This will prevent it being obscured by cleaning fluids and the stuff that get put under sink. The side wall position means if the plumbing fails its less likely to get wet.

You haven't mentioned the Postion of the tank and filters.

You haven't mentioned the cable size and mcb size and rcd arrangements.

You haven't mentioned the legal requirements of notification.

You haven't mention the MI's regarding load, local fused spurs double as a 2 pole isolation switch so it might be better to provide a fused spur as the switch with the correct fuse in.

 

[bernardgreen]

Hi,
I am installing an "instantaneous" undersink water heater~~~Can I place the switch in the cupboard under the sink?,

What if the thermostat / control of the heater fails and the water boils out of control ?. Would there still be safe access under the sink to the switch given there may be clouds of steam or scalding hot water in the area ?.

 

[MidAtlantian]

Chri5,

Thanks for your response. I'd seen comments that the switch had to be "above the work surface". Yes, I will mount it high on the side of the cupboard.

There isn't exactly a 'tank' with an instantaneous heater. And there is plenty of room under the sink for the heater, pipes, etc.

I'm using 6mm for a 6kw heater. The consumer unit has a 100ma RCD.

A local fused spur would be great, but it is way over 13 amps. I am not aware of residential fused spurs at 25 or 30 amps.

 

[MidAtlantian]

Hi bernardgreen,

While I can see your point, I wonder if then I need to consider access if the unit bursts into flames and I cannot enter the room! Especially since the consumer unit itself is in the same room!

If I can still enter the room, there would be the option that I turn it off at the consumer unit. But I would expect that that dramatic an incident would trigger the RCD as water and steam got to the electrics.

 

[Chri5]

6 kw

That's a lot of energy to replace a kettle


One I googled was a modest 1500w, hence the fspur suggestion.

I'd be tempted to back to back the switch, maybe have it (if cabinet layout allows) in the cupboard next to the sink and heater components, thus reducing all wet risks due to leaks, filter change etc..

 

[ban-all-sheds]

6 kw

That's a lot of energy to replace a kettle

But not a lot compared to the DHW output of a combi boiler.

Methinks this device is to allow the sink to be filled with hot water, not provide near-boiling water for making tea....

 

[MidAtlantian]

Chri5,

Thanks. Yes this is NOT to boil water: it is to have hot water to wash hands, paint brushes, and get hot water to mop the floor.

Back to back sounds interesting, but apart from the drawers next to the sink, I'd be concerned that in an emergency, one might not think to look in the next cupboard for the switch.

Could I ask you to look at my other question? About putting multiple cables in a single channel in a stone wall? No one seems interested in it!

Thanks,
MidAtlantian

 

[Chri5]

Grouping factor could apply, but we are talking three or under cables and each cable has decent headway.

I wouldn't worry about it unless you know the cable load will be very near cable tolerance.

If you are worried make the chase 40mm wide and clip direct to brick with cables flat to brick rather than all on top in one deeper thiner chase.

 

[RF Lighting]

I would have thought adjacent to the heater would be the ideal position for the isolator.

If some how both stats fail and the unit ejects boiling water then it's time to bang the main switch in the CU off.